French far-right National Front party leader Marine Le Pen arrives for a meeting at the party's headquarters west of Paris on May 27. / Jacques Brinon, AP

by Kim Hjelmgaard, USA TODAY

by Kim Hjelmgaard, USA TODAY

LONDON - As popular uprisings go, for a 28-nation bloc run from Brussels, this one was pretty cataclysmic. European Parliament election results, which the region is still digesting, reflect a wave of voter disenchantment with the area's most ambitious post-WWII policy idea - the European Union.

Over the weekend, Europe's centrists took a beating at the hands of anti-establishment parties in Britain, Belgium, Denmark, France and Greece.

"Too big, too bossy, too interfering" is the lesson that British Prime Minister David Cameron vowed to learn about the EU after his party's drubbing.

In Britain, the United Kingdom Independence Party, which has campaigned aggressively for an EU exit, topped the national poll with 27.5% of the vote, a result UKIP's leader Nigel Farage called "the most extraordinary result in British politics in 100 years." It has been a century since any group in the U.K. other than the Conservative or Labor Parties won a national election.

Across the English Channel, France's far-right National Front party, run by Marine Le Pen, scored 25% - a victory that French Prime Minister Manuel Valls called a "shock, an earthquake."

It remains to be seen how grave a moment this electoral rout will be for the grand European dream of ever-increasing economic, social and territorial cohesion. Though it's true that Euro-skeptic parties have suddenly been upgraded, established pro-EU parties are likely to remain the biggest groups in the parliament, which passes EU-wide laws, oversees the lawmaking European Commission and manages the EU's $200 billion budget.

But the EU has taken a stunning hit to its credibility and some of the long-held assumptions about the union may be just that: assumptions. The free movement of labor, the security that has followed closer integration and other EU verities are axiomatic for some. For others, they are a cause for deep alarm. The EU as an idea is too abstract and unwieldy to be held tight in the way the nation-state can.

Since the start of the week, leaders across Europe have scrambled to get into damage-control mode.

Britain's Cameron said Tuesday the results showed that, for Britain, it couldn't just be "business as usual," He called for drastic changes to reduce EU power. French President Francois Hollande said he stood by the EU's many joint policies but vowed to redouble efforts to ignite his nation's economy.

Karel Lannoo, chief executive of the Center for European Policy Studies, a Brussels-based think-tank, says the poll results don't offer much optimism about the EU's ability to work effectively. "This is a retrograde reaction," he says. "We have just elected 100 Europhobes to provide contra-ammunition against the EU project any time they can."

Lannoo says pushing through legislation will almost certainly be more difficult, and the machinery of decision-making in the European Parliament will look like one more familiar to Americans.

"Brussels will become a big Washington, D.C.," he says, "a kind of place where lobbyists are extremely active, where (lawmaking) is always paralyzed and full of horse trading."

Hjelmgaard reports for USA TODAY from London. Follow him on Twitter: @khjelmgaard